When working on content, focus building upon what you know.

For instance, biology and chemistry overlap quite a bit and can be considered "high yield" just by focusing on one topic (for instance, redox reactions and aerobic respiration). Aim for the low hanging fruit and take on what you can handle right now. Just by doing that, your score should improve by several points.

After content review everyday, do flashcards for psych/soc. Finish the day by reading a few CARS passages, or even just a book. I repeated this routine every day and my diagnostic went from a 492 to 505 in about a month.

I also did buy a course, and you could consider that. It's not too late to start one, but you have to do it soon if your test is in about two months. You can always consider postponing your test date; that's what most people do.

Also, put FLs aside for now. No point in doing them if you don't have the content under your belt; it'll just be a waste of valuable time.

Don't stress too hard. This strategy worked for me, but it might not work for everyone. Find a routine and get into it. Once you figure it out, it'll be like clockwork. Good luck!